There are only two vehicles that can generate resources.
There is a resource base, and a destroyer-size resource ship.
Both of these are really easy to hit and have little room left over for defences, so they have to protected very well, just like planets.
The ship will generate a little more than 200 resources per turn, which resource depends on what kind of plug-in module you have. The base can hold four or five plug-ins, and produces that much more.
That keeps the military & civilian sides separate, so the nomads don't grow exponentially
They have to decide how much of the budget to put towards building more resources & how much to spend on military. The nomads will also tend to lag behind technologically with no research, so they're gonna have to steal tech.